When mentioning end caps, many people think of pipe caps. In fact, although end caps and pipe caps look somewhat similar, they have obvious differences in design, manufacturing, application, and standards. Correct selection and use of these two products are important for ensuring the safe operation of equipment and extending its service life.
　　1. Different Definitions
　　End cap: Also known as an end cover, it is a component used to close the end of a container, isolating the internal and external media. According to the surface shape, end caps can be divided into convex, conical, flat, and combined types. Convex end caps include spherical, elliptical, dished, and edge-less spherical end caps.
　　Pipe cap: Also known as end cap, plug, cover, pipe cover, or blind cap, it is a pipe fitting welded to the pipe end or installed on the external thread of the pipe end to cover and block the pipe. It is used to close pipelines and serves the same function as a pipe plug. Its form is similar to a blind flange, but welded pipe caps are non-removable. Pipe caps include convex pipe caps, conical shells, reducer sections, flat covers, and designs with constricted openings. Convex pipe caps include hemispherical, elliptical, dished, and crown-shaped pipe caps. From a stress perspective, the performance of convex pipe caps decreases from hemispherical caps downward, but from a manufacturing difficulty perspective, they become easier to produce.
　　3. Different Pressure Bearing Capacities
　　Pipe cap: Suitable for low-pressure conditions below PN16, usually not used for high-risk media (such as flammable or toxic gases). Designed according to pipe fitting pressure ratings, generally matching the pipeline system's Class or PN rating (e.g., Class 150, PN16) without separate strength calculations, but must match the pipeline pressure rating.
　　End cap: Has a wide pressure range, from PN16 to PN400 or even higher, requiring stress analysis and burst testing for verification. Calculated according to pressure vessel design standards (such as ASME VIII, GB 150), considering internal pressure, external pressure, wall thickness, and other factors. Strict requirements for materials and welding processes, requiring material reports and non-destructive testing (UT/RT) certificates.
　　4. Different Application Fields
　　End cap: Mainly used at the ends of various pressure vessels, storage tanks, boilers, reactors, towers, and other equipment. It is an indispensable important component of pressure vessels and directly relates to the safety performance of the pressure vessel.
　　Pipe cap: Mainly used at the ends of various pipeline systems to close the pipeline, prevent media leakage or foreign object entry, and is also often used for temporarily closing unused pipelines.
　　5. Different Connection Methods
　　1. Connection methods of pipe caps:
　　Butt weld: The pipe cap's end is beveled and aligned with the pipe end, then connected by welding. This is the most common connection method in pipeline systems that bear higher pressure and temperature, offering high strength and sealing.
　　Socket weld: One end of the pipe cap is made into a socket, the pipe is inserted into the socket, then circumferential welding is performed. Socket welding is suitable for medium and small diameters and medium to low pressure pipeline systems, easy to install but with lower strength than butt weld.
　　Threaded: One end of the pipe cap is processed with internal threads and screwed onto the external threads at the pipe end. Threaded connections are suitable for small diameter, low-pressure pipeline systems, easy to disassemble but with relatively lower sealing and strength.
　　2. Connection methods of end caps:
　　Welded connection: The connection between the end cap and the pressure vessel shell must be welded to ensure the strength and sealing of the entire vessel. Common welding methods include butt welding and fillet welding, with specific forms depending on the shape of the end cap and the structure of the shell.
　　Summary
　　Therefore, when selecting and using, it is necessary to distinguish between end caps and pipe caps based on specific application scenarios and design requirements. The ends of pressure vessels must use end caps that comply with pressure vessel standards, while the ends of pipelines are usually closed with pipe caps that meet pipeline fitting standards. Pipe caps have more diverse connection methods and can be selected according to the specific needs of the pipeline system (such as pressure, media, diameter, and whether frequent disassembly is required). As a key component of pressure vessels, end caps are almost always welded to meet the strength and safety requirements of pressure vessels.

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